In recent years, the consumers' pursuit for ultra-bright paper has pushed the market demands for more products with a brightness of 90-110 in ISO standards. In order to produce these ultra-high brightness products, optical brightener agents (OBA's) or fluorescent whitening agents (FWA's) must be utilized.
OBA's or FWA's have chemical properties that absorb light in the ultra-violet region (340-370 nm) and then re-emitting it back into the visible spectrum, usually in the color blue or indigo (420-470 nm). The absorption and re-emission happen at a rapid pace unlike the slow phosphorescence behaviour. The newly added blue light compensates the yellowness of paper products and produces a net whitening effect that is observable to the naked eye.
There is an ongoing need for improved brightness with low cost and with greater stability of the optical properties, i.e. decreased reversion such as yellowing (caused by overdosage), photoyellowing, and higher retention rates.